Dataset: ASU Fragmentation – Landscape Fine-scale Complexity

In order to investigate the ecological effects of habitat area and patchiness on faunal community structure and dynamics of estuarine nekton, Artificial seagrass unit (ASU) landscapes were designed and deployed at a scale relevant to habitat fidelity of common fish and macroinvertebrates (days to weeks) in a temperate study system on the Oscar Shoal and an adjacent unnamed shoal (34°42′20" N to 34°41′60" N, 76°36′ 15" W to 76°35′17" W) in Back Sound, NC, USA during the summer of 2018. Both shoals were shallow (less than 0.5-meter depth at low tide) and historically supported expansive, ephemeral seagrass meadows (Peterson et al., 2001) that have been absent over the last decade. During 2018, these shoals had large expanses of sandy area speckled with small patches of seagrass (which were avoided during landscape siting) composed of a mixture of eelgrass, Zostera marina (Linnaeus 1753), and shoal grass, Halodule wrightii (Ascherson 1868) (Yeager et al., 2016). Both shoals were adjacent to deep boating channels between two large salt marsh complexes to the north (North River Marsh) and south (Middle Marsh).

The habitat features of ASUs have the potential to be modified by sediment burial or scouring after installation. Therefore, in July and September 2018, fine-scale habitat complexity metrics, including ASU canopy height and epiphyte biomass, were sampled along a transect from the edge to the center of the largest patch in each landscape. Along each transect, five ribbon clippings were taken per ASU and an additional five clippings were taken on the edge ASU, within 0.5 meters of the ASU-matrix interface. The number of ASUs sampled per landscape [mean of 6.81 ± 3.24 SD] differed based on percent cover and configuration. Each ASU ribbon was haphazardly selected and clipped at the sediment surface, then measured to the approximate above-sediment landscape canopy height. In the lab, epiphytes were scraped off each side of the ribbon, dried for 12 hours at 60 degrees C, then burned for 4 hours at 500 degrees C to determine ash content (Peterson and Heck, 2001). Ash-free dry epiphyte biomass (hereafter "epiphyte biomass") was calculated as dry weight minus ash weight, then divided by the surface area of the ribbon to obtain standardized epiphyte biomass (milligrams per square centimeter).

Known Issues:
Instrumental error in mass measurements results in some samples having negative weights when tin weights are subtracted from the dry weight or ash weight.

Several samples were lost partway through processing. A small number of sample labels were lost therefore the site from which they came is unknown. There is one set of samples that came from site 60 percent-0.59, but it is unknown which site replicate they came from (i.e., A or B).